1. Field of the Invention
The present invention relates to an electromagnetic clutch for respectively connecting and disconnecting a drive source to and from a driven device having a fixed hollow cylindrical projection and a rotatable shaft extending within the hollow projection in concentric relation thereto. More particularly, the present invention relates to an electromagnetic clutch suitable for use with a compressor used in an air-conditioning system installed on a motor vehicle, for example.
2. Description of the Prior Art
An electromagnetic clutch of the kind referred to above comprises a rotatable body made of magnetizable material. The rotatable body is disposed around a fixed hollow cylindrical projection of a driven device, such as a compressor for a cooler in concentric relation to the cylindrical projection and is drivingly connected to a drive source, such as an engine of a motor vehicle for rotation around an axis of a shaft of the driven device. The rotatable body has its inner peripheral surface faced to the cylindrical projection and opposite axial end faces. A bearing is disposed between the outer peripheral surface of the cylindrical projection and the inner peripheral surface of the rotatable body for supporting the rotatable body on the cylindrical projection.
An armature made of magnetizable material and connected to the shaft for rotation therewith is faced to one of the opposite axial end faces of the rotatable body, but is normally spaced therefrom by a suitable gap. The armature is movable between an engaging position where the armature is attracted and abuts against the one axial end face of the rotatable body to allow the rotation of the rotatable body by the drive source to be transmitted to the shaft and a disengaging position where the armature is spaced from the one axial end face of the rotatable body by the suitable gap to prevent the rotation of the rotatable body from being transmitted to the shaft. An exciting solenoid is associated with the armature to move the same between the engaging and disengaging positions in response to energization and deenergization of the solenoid.
The rotatable body has formed on its inner peripheral surface an annular shoulder adjacent to the one axial end face of the body. In addition, the cylindrical projection of the driven device has formed in its outer peripheral surface an annular groove at a location substantially radially opposite to the annular shoulder. A cylindrical cover member is disposed adjacent to the bearing for preventing leaked oil and grease from entering the gap between the armature and the one axial end face of the rotatable body. The cylindrical cover member includes a peripheral wall for covering the gap, and an annular end wall extending from an axial end of the peripheral wall remote from the bearing and cooperating with the peripheral wall to define a reservoire for the leaked oil and grease. The cylindrical cover member has an annular flared portion projecting substantially radially outwardly from the other end of the peripheral wall of the cover member. Upon the assembly of the electromagnetic clutch, the flared portion is clamped by and between the annular shoulder and an axial end of the bearing. Thus, the cylindrical cover member is fixedly mounted on the inner peripheral surface of the rotatable body. Thereafter, a snap ring is caused to pass through an opening defined by the annular end wall of the cover member toward the bearing, and is fitted in or snapped into an annular groove in the outer peripheral surface of the cylindrical projection of the driven device so that the bearing is held in position against axial movement.
With the prior art arrangement described above, the diameter of the opening defined by the annular end wall of the cylindrical cover member is required to have a size sufficient to enable the snap ring to pass through the opening. This makes it impossible to increase the radial length of the annular end wall of the cover member. Accordingly, the oil reservoir defined by the peripheral wall and the annular end wall of the cylindrical cover member cannot receive therein a considerable amount of oil and grease. In addition, in the case where the bearing has a small radial dimension between the inner and outer peripheral surfaces of the bearing, it is difficult and troublesome to fit the snap ring into the annular groove, because the cylindrical cover member is previously installed and the snap ring is required to pass through the opening defined by the annular end wall of the cover member.